Allocating a control channel for carrier aggregation

ABSTRACT

A user equipment (UE) is disclosed. The UE can monitor a set of physical downlink control channel (PDCCH) candidates defined in a search space Sk(L) at an aggregation level L∈{1,2,4,8} for a subframe (k). The UE can decode a PDCCH of the set of PDCCH candidates according to a downlink control information (DCI) format.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/482,107, filed Sep. 10, 2014, which is a continuation of U.S. patentapplication Ser. No. 13/969,966, filed Aug. 19, 2013, which is acontinuation of U.S. patent application Ser. No. 13/275,608 filed Oct.18, 2011, which is a continuation of Ser. No. 12/967,652 filed on Dec.14, 2010, which claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/330,837, filed on May 3, 2010, all of which arehereby incorporated by reference for all purposes.

BACKGROUND

Wireless mobile communication technology uses various standards andprotocols to transmit data between a base transceiver station (BTS) anda wireless mobile device. In the third generation partnership project(3GPP) long term evolution (LTE) systems, the BTS is a combination ofevolved Node Bs (eNode Bs or eNBs) and Radio Network Controllers (RNCs)in a Universal Terrestrial Radio Access Network (UTRAN), whichcommunicates with the wireless mobile device, known as a user equipment(UE). Data is transmitted from the eNode B to the UE via a physicaldownlink shared channel (PDSCH). A physical downlink control channel(PDCCH) is used to transfer downlink control information (DCI) thatinforms the UE about resource allocations or scheduling related todownlink resource assignments on the PDSCH, uplink resource grants, anduplink power control commands. The PDCCH can be transmitted prior to thePDSCH in each subframe transmitted from the eNode B to the UE.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the disclosure will be apparent from thedetailed description which follows, taken in conjunction with theaccompanying drawings, which together illustrate, by way of example,features of the disclosure; and, wherein:

FIG. 1 illustrates a block diagram of radio frame resources inaccordance with an example;

FIG. 2 illustrates a block diagram of carrier aggregation in accordancewith an example;

FIG. 3 illustrates a block diagram of component carrier (CC) bandwidthsin accordance with an example;

FIG. 4 illustrates a block diagram of a downlink channel structure inaccordance with an example;

FIG. 5A illustrates a block diagram of a resource element groups (REGs)in a Resource Block (RB) in accordance with an example;

FIG. 5B illustrates a block diagram of a resource element groups (REGs)in a Resource Block (RB) in accordance with an example;

FIG. 6A illustrates a block diagram of scheduling component carrier (CC)data in accordance with an example;

FIG. 6B illustrates a block diagram of cross carrier scheduling of datain accordance with an example;

FIG. 7A illustrates a block diagram of control channel elements (CCEs)in a PDCCH search space in accordance with an example;

FIG. 7B illustrates a table with aggregation levels, sizes, andcandidates of a PDCCH search space in accordance with an example;

FIG. 8 illustrates a block diagram of control channel elements (CCEs)and candidates in a search space in accordance with an example;

FIG. 9 illustrates a block diagram of a search space utilizingtransmission modes in accordance with an example;

FIG. 10 illustrates a block diagram of a search space utilizingtransmission modes in accordance with an example;

FIG. 11 illustrates a block diagram of a search space utilizingtransmission modes and carrier indexes (CIs) in accordance with anexample;

FIG. 12 illustrates a block diagram of a search space utilizingtransmission modes, carrier indexes (CIs), and downlink controlinformation (DCI) sizes in accordance with an example;

FIG. 13 illustrates a block diagram of an evolved Node B (eNode B oreNB) and user equipments (UEs) in accordance with an example; and

FIG. 14 depicts a flow chart of a method for allocating a physicaldownlink control channel (PDCCH) to reduce a number of PDCCH candidatesin a search space on a user equipment (UE) in accordance with anexample.

Reference will now be made to the exemplary embodiments illustrated, andspecific language will be used herein to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended.

DETAILED DESCRIPTION

Before the present invention is disclosed and described, it is to beunderstood that this invention is not limited to the particularstructures, process steps, or materials disclosed herein, but isextended to equivalents thereof as would be recognized by thoseordinarily skilled in the relevant arts. It should also be understoodthat terminology employed herein is used for the purpose of describingparticular examples only and is not intended to be limiting. The samereference numerals in different drawings represent the same element.

EXAMPLE EMBODIMENTS

An initial overview of technology embodiments is provided below and thenspecific technology embodiments are described in further detail later.This initial summary is intended to aid readers in understanding thetechnology more quickly but is not intended to identify key features oressential features of the technology nor is it intended to limit thescope of the claimed subject matter. The following definitions areprovided for clarity of the overview and embodiments described below.

A system and method is provided for allocating a physical downlinkcontrol channel (PDCCH) to reduce a number of PDCCH candidates in asearch space for carrier aggregation on a user equipment (UE). A controlchannel element (CCE) aggregation level is selected for a PDCCHallocation for each of a plurality of user equipments (UEs) at anevolved NodeB (eNB). A transmission mode is identified for each of aplurality of component carriers (CCs) associated with the PDCCH at theeNB. Each CC's downlink control information (DCI) is assigned into CCEsin a PDCCH search space starting at a CCE location based on the CC'stransmission mode and the CCE aggregation level for the UE receiving theCC. The eNode B can provide the allocation of the PDCCH and assignmentof the CCEs to a search space using a transmission mode to create moresearch spaces for the CCs of the UE. Using the transmission mode cangenerate up to eight additional search space starting locations bypartitioning the search space. The UE may use the carrier index (CI) orthe DCI size along with the transmission mode to assign the CCEs to aPDCCH search space.

After the CCEs are assigned to a PDCCH search space, the PDCCH can betransmitted to a UE. At the UE, the PDCCH can be searched by the UE foreach of the UE's CC's DCI. The UE may use the transmission mode, thecarrier index (CI), and/or the DCI size to efficiently search smallerPDCCH search spaces in the PDCCH.

Data in wireless mobile communication can be transmitted on the physical(PHY) layer by the eNode B (also commonly denoted as an enhanced Node B,evolved Node B, or eNB) to the user equipment (UE) using a generic longterm evolution (LTE) frame structure, as illustrated in FIG. 1. A radioframe 100 of a signal used to transmit the data is configured to have aduration, T_(f), of 10 milliseconds (ms). Each radio frame can besegmented or divided into ten subframes 110 i that are each 1 ms long.Each subframe can be further subdivided into two slots 120 a and 120 b,each with a duration, T_(slot), of 0.5 ms. The first slot (#0) 120 a caninclude a physical downlink control channel (PDCCH) 160 and a physicaldownlink shared channel (PDSCH) 166, and the second slot (#1) 120 b caninclude data using the PDSCH. Each slot for a component carrier (CC)used by the eNode B and the UE can include multiple resource blocks(RBs) 130 a, 130 b, 130 i, 130 m, and 130 n based on the CC frequencybandwidth. Each RB 130 i can include twelve 15 kHz subcarriers 136 (onthe frequency axis) and 6 or 7 orthogonal frequency-divisionmultiplexing (OFDM) symbols 132 (on the time axis) per subcarrier. TheRB uses seven OFDM symbols if a short or normal cyclic prefix isemployed. The RB uses six OFDM symbols if an extended cyclic prefix isused. The resource block can be mapped to 84 resource elements (REs) 140i using short or normal cyclic prefixing, or the resource block can bemapped to 72 REs (not shown) using extended cyclic prefixing. The RE canbe a unit of one OFDM symbol 142 by one subcarrier (i.e., 15 kHz) 146.Each RE can transmit two bits 150 a and 150 b of information in case ofquadrature phase shift keying (QPSK) modulation. Other types ofmodulation may be used as well. For instance, when bi-phase shift keying(BPSK) modulation is used, then only a single bit of information istransmitted.

In carrier aggregation (CA), CCs for a Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access Network can becombined together to form a larger bandwidth for the UE, as illustratedin FIG. 2. For example, the UMTS may have a system bandwidth 210 of 100MHz in a frequency spectrum 216 with each CC 212 having a 20 MHzbandwidth. Each CC may comprise a plurality of subcarriers 214. Some UEs230 may use the entire 100 MHz system bandwidth by aggregating five 20MHz CCs together to achieve a 100 MHz UE bandwidth 220. In anotherexample, two UEs 232 a and 232 b each with a 40 MHz bandwidth capabilitymay each use two 20 MHz CCs together to achieve a 40 MHz UE bandwidth222 for each UE. In another example, each UE 234 a, 234 b, 234 c, 234 d,and 234 e may use a single 20 MHz CC to achieve a 20 MHz UE bandwidth224. The CCs at an eNode B may be aggregated for some UEs while otherUEs may use a single CC during the same interval. For example, one UEwith a 40 MHz bandwidth may be configured while three UEs that each usea single 20 MHz CC are employed in a 100 MHz bandwidth system (notshown). Carrier aggregation allows the bandwidth for a UE to be adjustedand adapted based on the system limitations, the UEs capabilities andbandwidth requirements, the bandwidth available to the system and/orloading on the system.

Each UMTS may use a different carrier bandwidth, as illustrated in FIG.3. For example, the LTE Release 8 (Rel-8) carrier bandwidths and Release10 (Rel-10) CC bandwidths can include: 1.4 MHz 310, 3 MHz 312, 5 MHz314, 10 MHz 316, 15 MHz 318, and 20 MHz 320. The 1.4 MHz CC can include6 RBs comprising 72 subcarriers. The 3 MHz CC can include 15 RBscomprising 180 subcarriers. The 5 MHz CC can include 25 RBs comprising300 subcarriers. The 10 MHz CC can include 50 RBs comprising 600subcarriers. The 15 MHz CC can include 75 RBs comprising 900subcarriers. The 20 MHz CC can include 100 RBs comprising 1200subcarriers.

Each subframe of a CC may include downlink control information (DCI)found in a PDCCH, as illustrated in FIG. 4. The PDCCH in the controlregion may include one to three columns of the first OFDM symbols ineach subframe or RB. The remaining 11 to 13 OFDM symbols in the subframemay be allocated to the PDSCH for data. The control region can includePhysical Control Format Indicator Channel (PCFICH), physical hybridautomatic repeat request (hybrid-ARQ) indicator channel (PHICH), and thePDCCH. The control region has a flexible control design to avoidunnecessary overhead. The number of OFDM symbols in the control regionused for the PDCCH can be determined by the control channel formatindicator (CFI) transmitted in the Physical Control Format IndicatorChannel (PCFICH). The PCFICH is located in the first OFDM symbol of eachsubframe. The PCFICH and PHICH can have priority over the PDCCH, so thePCFICH and PHICH are scheduled prior to the PDCCH.

The CFI and the PDCCH can be illustrated by the example of FIG. 4.Subframe A 110 a, including slot #0 120 a and slot #1 120 b, has a CFI410 equal to one indicating the first column of OFDM symbols in a CC'ssubframe A are used for the PDCCH 420 and the remaining 13 columns ofOFDM symbols (in short cyclic prefixing) are used for the PDSCH 430.Each CC includes a plurality of subcarriers 436 mapped to a plurality ofRBs. Subframe B 110 b has a CFI 412 equal to three indicating the firstthree columns of OFDM symbols in a CC's subframe B are used for PDCCH422 and the remaining 11 columns of OFDM symbols (in short cyclicprefixing) are used for PDSCH 432. Subframe C 110 c has a CFI 414 equalto two indicating the first two columns of OFDM symbols in a CC'ssubframe C are used for PDCCH 424 and the remaining 12 columns of OFDMsymbols (in short cyclic prefixing) are used for PDSCH 434. In theexample illustrated in FIG. 4, the subframe A is followed by subframe Band subframe C in time 400.

DCI can be mapped to the PDCCH using resource element groups (REGs)except both the PCFICH and PHICH, as illustrated in FIG. 5A. REGs can beused for defining the mapping of control channels to resource elements.A RB may include reference signal REs (reference signal OFDM symbols)522 used for transmitting reference signals for a specific antenna portand unused REs (unused OFDM symbols) 520 not used for transmission onthe specific port, which allow other antenna ports to transmit theirreference signals. The number of reference signal REs and unused REsused in the RB can depend on the number of antenna ports. REGs can beused to map control channels to the remaining resource elements. REGsinclude a symbol quadruplet or four REs that do not include referencesignal REs.

For example, a two antenna port configured RB 502 with a CFI=3 caninclude seven REGs 512 in the control region or seven REGs used for thePDCCH (if no REGs are used for PCFICH and PHICH), as illustrated in FIG.5A. A four antenna port configured RB 504 with a CFI=3 can include sixREGs in the control region or six REGs used for the PDCCH (if no REGsare used for PCFICH and PHICH), as illustrated in FIG. 5B. The REGs inthe control region of the RBs for a CC can comprise the PDCCH. Each CCEused in the PDCCH can include 9 REGs. The PDCCH can be formed with oneor more successive CCEs. A plurality of PDCCHs can be transmitted in asingle subframe.

The PDCCH in the control region of a subframe can provide DCI thatinforms the UE about scheduling on a CC related to downlink resourceassignments on the PDSCH, uplink resource grants, and uplink powercontrol commands. Each CC can provide scheduling in the PDCCH (in thecontrol region) for the data in the PDSCH, as illustrated in FIG. 6A. APDCCH in the control region 620 a for CC 1 on CC 1 600 a can provide thescheduling for a PDSCH 630 a for CC 1 in a subframe 610 a. A PDCCH inthe control region 620 b for CC 2 on CC 2 600 b can provide thescheduling for a PDSCH 630 b for CC2. A PDCCH in the control region 620c for CC 3 on CC 3 600 c can provide the scheduling for a PDSCH 630 cfor CC3. The subframes 610 a, 610 b, and 610 c for the CC 1, CC 2, andCC 3 may represent the same time duration. Each CC can provide its ownPDCCH for the PDSCH scheduling.

In another example, one CC can provide the PDCCH for scheduling downlinkresource assignments on the PDSCH of another CC, as illustrated in FIG.6B. The DCI of one CC can be included or mapped to another CC's PDCCH.For example, the control region for CC 1 622 a, the control region forCC 2 622 b, and the control region for CC 3 622 c can be contained inthe PDCCH on CC 1 600 a. The control region for CC 1 provides thescheduling for the PDSCH 632 a on CC 1, the control region for CC 2provides the scheduling for the PDSCH 632 b on CC 2, and the controlregion for CC 3 provides the scheduling for the PDSCH 632 c on CC 3.3GPP LTE systems can provide for cross carrier scheduling of the PDSCHwhere the PDCCH is transmitted on a CC different from the CCtransmitting the PDSCH.

The eNode B may schedule the CCEs in the PDCCH and code the DCI based ona predetermined process, and the UE may receive the transmission and maysearch for the DCI in the PDCCH and decode the DCI based on thepredetermined process. The PDCCH can be formed with one or moresuccessive CCEs. The total number of CCEs in the PDCCH can vary in everysubframe k, where k∈{0,1,2,3,4,5,6,7,8,9}, of a radio frame. The numberof CCEs in the PDCCH can be represented by N_(CCE,k).

For example, the PDCCH 700 can include 86 CCEs 710, as illustrated inFIG. 7A. Each CCE may include nine REGs 512 a, 512 b, 512 c, 512 d, 512e, 512 f, 512 g, 512 h, and 512 i. Each REG may include four REs 140 a,140 b, 140 c, and 140 d.

The PDCCH can provide control information to multiple UEs in a cell foreach subframe k. The UE can perform blind decoding since the UE may beaware of the detailed control channel structure, including the number ofcontrol channels (CCHs) and the number of CCEs to which each controlchannel is mapped. Multiple PDCCHs can be transmitted in a singlesubframe k which may or may not be relevant to a particular UE. Becausethe UE does not know the precise location of the DCI information in aPDCCH, the UE searches and decodes the CCEs in the PDCCH until the DCIis found for the UE's CCs. The PDCCH can be referred to as a searchspace. The UE finds the PDCCH specific to the UE (or the UE's CCs) bymonitoring a set of PDCCH candidates (a set of consecutive CCEs on whichthe PDCCH could be mapped) in a PDCCH search space in each subframe.

The UE can use a Radio Network Temporary Identifier (RNTI) assigned tothe UE by the eNode B to try and decode candidates. The RNTI can be usedto demask a PDCCH candidate's cyclic redundancy check (CRC) that wasoriginally masked by the eNode B using the UE's RNTI. If the PDCCH isfor a specific UE, the CRC can be masked with a UE unique identifier,for example a Cell-RNTI (C-RNTI). If no CRC error is detected the UE candetermine that a PDCCH candidate carries the DCI for the UE. If a CRCerror is detected then the UE can determine that PDCCH candidate doesnot carry the DCI for the UE and the UE can increment to the next PDCCHcandidate. The UE may increment to the next PDCCH candidate in thesearch space based on the CCE aggregation level. The CCE aggregationlevel will be discussed more fully in the following paragraphs.

To reduce the burden and improve the process performance of the UE, thePDCCH can be composed of a search space within the PDCCH to improvesearching and decoding of the PDCCH candidates. Each search space canhave a starting address determined by the RNTI. The PDCCH can be dividedinto a common search space 710, which can provide scheduling informationfor system information received by a group of UEs in a cell, and a UEspecific space 712 allocated to control information for a particular UE.The common search space can be composed of the first 16 CCEs (CCE 0through CCE 15) the remaining CCEs may to allocated to the UE specificspace 712.

The number of CCEs used to transmit one piece of control information canbe determined according to the receiving quality of the PDCCH allocatedto a UE or the channel quality of the UE, and the number of CCEs isreferred to as a CCE aggregation level or an aggregation levelL∈{1,2,4,8}. The aggregation level can be used to determine the size ofa search space or the number of CCEs forming a search space, and/or thenumber of control channel (CCH) candidates in a search space, asillustrated in table 702 of FIG. 7B.

In another example, if a search space 800 includes 8 CCEs 810, 812, 814,816, 818, 820, 818, and 820, the total number of CCH candidates that canbe decoded may be 15. Eight CCH candidates 830, 832, 834, 836, 838, 840,842, and 844 can represent the candidates that can be decoded with anaggregation level of one (L=1). The UE can increment through the searchspace by the aggregation level until the DCI for the CCs of the UE isfound. Four CCH candidates 846, 848, 850, and 852 can represent thecandidates that can be decoded with an aggregation level of two (L=2).Two CCH candidates 854 and 856 can represent the candidates that can bedecoded with an aggregation level of four (L=4). One CCH candidate 858can represent the candidates that can be decoded with an aggregationlevel of eight (L=8). Searching and decoding the CCH candidates (PDCCHcandidates) for the DCI in each subframe can be referred to as blinddecoding.

Each decode takes a certain amount of time to process. The UE may have alimited number of blind decodes (for the candidates in the PDCCH)available in the timeframe allotted for decoding before the PDSCH ornext subframe is transmitted for processing. For example, a UE may beable to handle up to 44 blind decodes before the PDSCH or next subframeis transmitted for processing. When the number (e.g., 300) of CCHcandidates for an aggregation level is greater than a blind decode limitfor the UE, then the UE may fail to obtain the CCH information and failto process the PDSCH. Reducing the number of potential search spaces canbe used to assist the UE to find and decode the DCI in the PDCCHefficiently and within an available time limit.

The 3GPP transport stream (TS) 36.2211 V8.4.0 defines a PDCCH allocationprocedure for a search space S_(k) ^((L)). A starting address of a UEspecific search space that contains the DCI for a UE can be allocated byEquation 1 defined based on an aggregation level L∈{1,2,4,8}, whereY_(k) is defined by Equation 2, N_(CCE,k) is the total number of CCEs ina k^(th) subframe (k∈{=0,1,2,3,4,5,6,7,8,9}), i=0, . . . , L−1 is aconstant, m=0, . . . , M^((L))−1, and M^((L)) is the number of PDCCHcandidates to monitor in a given search space.S _(k) ^((L)) =L·{(Y _(k) +m)mod └N _(CCE,k) /L┘}+i  [Equation 1]

The variable Y_(k) is defined by Equation 2, where Y⁻¹=n_(RNTI)≠0,n_(RNTI) is the RNTI number assigned to a UE, A=39827, D=65537,k=└n_(s)/2┘, and n_(s)(n∈{0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19}) is the slotnumber within the radio frame.Y _(k)=(A·Y _(k−1))mod D  [Equation 2]

The 3GPP TS 36.2211 V8.4.0 assignment procedure does not involve CCaggregation. 3GPP Rel-8 and Rel-9 do not support the scheduling of crosscarriers and the UE is allocated one C-RNTI in CC aggregation. Using theRNTI and aggregation level of a UE maps the DCI of a UE to a single UEsearch space. As UE bandwidths increase, the number of PDCCH increase,the number of CCs increase, and the PDCCH search space sizes increase,then the number of decodes used to successfully decode PDCCH candidateswill increase.

Instead of using a single search space for a UE, the search spaces maybe further partitioned to decrease the search space size for a CC on aUE to reduce the number of blind decodes of PDCCH candidates and allowmore efficient decoding of PDCCH candidates. In accordance with oneembodiment of the present invention, the starting address of a UEspecific search space can utilize the partial or full combinations ofthe transmission (TX) modes (T_(c,m)) for a carrier (c), the carrierindex (CI) in the DCI format, and the DCI size (S) of different crosscarriers. The total possible number of search spaces created using themethod can be a product of the transmission (TX) modes (T_(c,m)) for acarrier (c), the carrier index (CI) in the DCI format, and the DCI size(S).

The eNode B can identify at least one value associated with each CC'sPDCCH, where the at least one value represents at least one of atransmission mode for the CC, the carrier index in the DCI format,and/or the DCI size. The eNode B can assign or map the CC's controlinformation (e.g., DCI) into CCEs in a search space based on the atleast one value associated with the CC. The UE can receive thetransmitted control channel (e.g., PDCCH) from the eNode B. The UE cansearch for the selected CC's control information in a search space usingthe CC's value and the CCE aggregation level for the UE receiving theselected CC. The UE can decode each control channel candidate in thesearch space until a validly decoded control channel candidate isdecoded or until all validly decoded control channel candidates in asearch space are decoded. The CC's control information, such as the DCI,may be obtained from the validly decoded control channel candidate.

In one embodiment, the eNode B can signal the transmission mode to theUE via a layer three communication link, such as Radio Resource Control(RRC) signaling, in advance of sending the PDCCH for a subframe. Thetransmission modes for PDSCH reception can include 8 modes: Mode 1(single antenna port, port 0), mode 2 (transmit diversity), mode 3(large-delay Cyclic Delay Diversity (CDD)), mode 4 (closed-loop spatialmultiplexing), mode 5 (multi-user multiple-input and multiple-output(MU-MIMO)), mode 6 (closed loop spatial multiplexing, single layer),mode 7 (single antenna port, UE-specific reference signal (RS) (port5)), and mode 8 (single or dual-layer transmission with UE-specific RS(ports 7 and/or 8)). The transmission mode can be changed per subframevia RRC signaling. Usually the transmission changes slowly. Changes inthe transmission mode may be based on changes in the environment thatthe UE is operating. Each CC used by the UE can have independenttransmission modes from other CCs. For a system with eight availabletransmission modes, up to eight additional search spaces for each UE maybe partitioned using the transmission modes for scheduling andsearching. The DCI size, which can also be used for scheduling andsearching, can be related to transmission modes and can be determinedfrom the transmission mode.

The carrier index (CI) can be CIF values or the index of sorted CIFvalues at the ascending order. The eNode B can configure the CIF valuesof each CC to UE via Radio Resource Control (RRC) signaling prior to thetransmission of the PDCCH for the subframe. The CI can change dependingon RRC reconfiguration. Other information transmitted by RRC signalingmay also be used for scheduling and searching PDCCH search spaces.

The variable Y_(k) can be modified to utilize at least one of thetransmission modes (T_(c,m)), the carrier index (CI), and/or the DCIsize (S) input parameters for the search space. Using an existing PDCCHassignment procedure and the transmission modes (T_(c,m)), Y_(k) can bedefined by Equation 3 to increase the number of starting addresses forsearch spaces based on the transmission mode, where Y⁻¹=n_(RNTI)≠0,A=39827, D=65537, k=└n_(s)/2┘, and n_(s) is the slot number within theradio frame.Y _(k) A·(Y _(k−1)+ƒ(T _(c,m)))] mod D  [Equation 3]

The ƒ(T_(c,m)) can be a function of transmission modes for a carrier(c). The carrier (c) can be a CC used by the UE. The ƒ(T_(c,m)) can bean integer based on the transmission modes (T_(c,m)). Equation 3 can beused to distinguish individual PDCCH search spaces for the different CCsin carrier aggregation. Equation 3 can specify that the PDCCHs with thesame transmission modes can be located in a shared search space and thePDCCHs having different transmission modes can be located in andifferent shared search space. The DCI for a carrier may be allocatedand mapped by an eNode B to CCEs in the PDCCH based on the transmissionmode.

For example, the PDCCH on a subframe 610 for multiple CCs (600 a-600 d)may be transmitted by CC 1 660 a, referred to as PDCCH1 920, asillustrated in FIG. 9. A first transmission mode search space 950starting location for a 1st transmission mode 940 on an independentsearch space on PDCCH1 918 may be calculated to be at a CCE location x962. The independent search space on PDCCH1 may have N CCEs (N_(CCE,k))970 for a subframe (k).

A PDCCH 922 for CC 1 with the first transmission mode may be assigned tothe first transmission mode search space beginning at the CCE locationx. The PDCCH for CC 1 can provide the PDSCH 972 scheduling for CC 1. APDCCH 924 for CC 2 600 b with the first transmission mode may beassigned to the first transmission mode search space 950 at a CCElocation after the PDCCH for CC 1. The PDCCH for CC 2 can provide thePDSCH 974 scheduling for CC 2.

In one embodiment, the PDCCHs may be scheduled in a search space basedon the order in which the PDCCHs are processed by an eNode B, and notnecessarily based on a CC number or the RNTI. In another embodiment, thePDCCHs with the same transmission mode may be assigned to a search spacein any order determined by the eNode B.

A second transmission mode search space 952 starting location for asecond transmission mode 942 on the independent search space on PDCCH1may be calculated to be at a CCE location s 964. A PDCCH 926 for CC 3660 c having the second transmission mode may be assigned to the secondtransmission mode search space beginning at the CCE location s. ThePDCCH for CC 2 can provide the PDSCH 976 scheduling for CC 3. A thirdtransmission mode search space 954 starting location for a thirdtransmission mode 944 on the independent search space on PDCCH1 918 maybe calculated to be at a CCE location v 966. A PDCCH 928 for CC 4 600 dwith the third transmission mode may be assigned to the thirdtransmission mode search space beginning at the CCE location v. ThePDCCH for CC 4 can provide the PDSCH 978 scheduling for CC 4. A fourthtransmission mode search space 954 with a starting location for a fourthtransmission mode on the independent search space on PDCCH1 may becalculated to be at a CCE location y 968 when a PDCCH for a fourthtransmission mode is used. In the illustration of FIG. 9, the PDCCHs forthe CCs have an aggregation level of two. The first transmission mode,the second transmission mode, the third transmission mode, and thefourth transmission mode does not refer to a mode 1, a mode 2, a mode 3,a mode 4, but the terms first, second, third, and fourth are used todistinguish between the available transmission mode that is used.

The UE may search the independent search space on PDCCH1 918 for thePDCCH for each CC using the existing PDCCH searching procedure and thetransmission modes (T_(c,m)). The transmission mode for a CC can betransmitted to the UE by RRC signaling prior to the subframetransmission. The PDCCH 922 for CC 1 600 a can be searched in the firsttransmission mode search space 950 until the DCI for the CC 1 is validlydecoded. Likewise, the PDCCH 924 for CC 2 600 b can be searched in thefirst transmission mode search space, the PDCCH 926 for CC 3 600 c canbe searched in the second transmission mode search space 952, and thePDCCH 928 for CC 3 600 c can be searched in the third transmission modesearch space 954.

In another example, the PDCCH for a subframe 610 for multiple CCs (600a-600 c) may be transmitted by CC 1 660 a, referred to as PDCCH1 1020,as illustrated in FIG. 10. A same transmission mode search space 1050starting location for a same transmission mode 1040 as CC 1 on anindependent search space on PDCCH1 1018 may be calculated to be at a CCElocation x 1062. The independent search space on PDCCH1 may have N CCEs(N_(CCE,k)) 1068 for a subframe (k). A PDCCH 1022 for CC 1 with the sametransmission mode as CC 1 may be assigned to the same transmission modesearch space beginning at the CCE location x. The PDCCH for CC 1 canprovide the PDSCH 1072 scheduling for CC 1.

A first PDCCH 1024 for CC 2 600 b with the same transmission mode as CC1 may be assigned to the same transmission mode search space 1050 at aCCE location after the PDCCH for CC 1, such as x+2 in this example. Thefirst PDCCH for CC 2 can provide the first PDSCH 1074 scheduling for CC2. A first different transmission mode search space 1052 startinglocation for a first different transmission mode 1042 that is differentfrom the transmission mode of CC 1 on the independent search space onPDCCH1 1018 may be calculated to be at a CCE location s 1064. A secondPDCCH 1026 for CC 2 with the first different transmission mode may beassigned to the first different transmission mode search space beginningat the CCE location s. The second PDCCH for CC 2 can provide the secondPDSCH 1076 scheduling for CC 2.

A second different transmission mode search space 1054 having a startinglocation for a second different transmission mode 1044 that is differentfrom the transmission mode of CC 1 on the independent search space onPDCCH1 may be calculated to start at a CCE location v 1066. A PDCCH 1028for CC 3 600 c with the second different transmission mode may beassigned to the second different transmission mode search spacebeginning at the CCE location v 1066. The PDCCH for CC 3 may have anaggregation level of four. The PDCCH for CC 3 can provide the PDSCH 1078scheduling for CC 3.

The variable Y_(k) can be modified to utilize the transmission modes(T_(c,m)) and the carrier index (CI) input parameters to further segmentthe search space. Using an existing PDCCH assignment procedure, thetransmission modes (T_(c,m)), and the carrier index (CI), Y_(k) can bedefined by equation 4 to increase the number of starting addresses forsearch spaces based on the transmission mode and CI, whereY⁻¹=n_(RNTI)≠0, A=39827, D=65537, k=└n_(s)/2┘, and n_(s) is the slotnumber within the radio frame.Y _(k) A·(Y _(k−1)+ƒ(CI,T _(c,m)))] mod D  [Equation 4]

The ƒ(CI,T_(c,m)) can be a function of transmission modes for a carrier(c) and the carrier index (CI) in the DCI formats. The ƒ(CI,T_(cm)) canbe an integer based on the transmission modes (T_(c,m)) and the carrierindex (CI). The DCI for a carrier may be allocated and mapped by aneNode B to CCEs in the PDCCH based on the transmission mode and thecarrier index.

For example, the PDCCH on a subframe 610 for multiple CCs may betransmitted by CC 1 600 a, referred to as PDCCH1 1120, as illustrated inFIG. 11. A same transmission mode and carrier index search space 1150starting location for a same transmission mode and carrier index 1140 asCC 1 on an independent search space on PDCCH1 1118 may be calculated tobe at a CCE location x 1162. The independent search space on PDCCH1 mayhave N CCEs N_(CCE,k)) 1170 for a subframe (k). A first PDCCH 1122 forCC 1 with the same transmission mode and carrier index as CC 1 may beassigned to the same transmission mode and carrier index search spacebeginning at the CCE location x. The first PDCCH for CC 1 can providethe first PDSCH 1172 scheduling for CC 1. A second PDCCH 1124 for CC 1with the same transmission mode and carrier index as CC 1 may beassigned to the same transmission mode and carrier index search space atthe CCE location after the first PDCCH for CC 1. The second PDCCH for CC1 can provide the second PDSCH 1174 scheduling for CC 1.

A first different transmission mode and/or carrier index search space1152 starting location for a first different transmission mode and/orcarrier index 1142 different from the transmission mode and/or carrierindex of CC 1 on the independent search space on PDCCH1 may becalculated to be at a CCE location j 1164. A first PDCCH 1126 for CC 2600 b with the different transmission mode and/or carrier index as CC 1may be assigned to the first different transmission mode and/or carrierindex search space beginning at the CCE location j. The first PDCCH forCC 2 can provide the first PDSCH 1176 scheduling for CC 2. A secondPDCCH 1128 for CC 2 with the first different transmission mode and/orcarrier index may be assigned to the first different transmission modeand/or carrier index search space at the CCE location after the firstPDCCH for CC 2. The second PDCCH for CC 2 can provide the second PDSCH1178 scheduling for CC 2.

A second different transmission mode and/or carrier index search space1154 starting location for a second different transmission mode and/orcarrier index 1144 different from the transmission mode and/or carrierindex of CC 1 on the independent search space on PDCCH1 may becalculated to be at a CCE location g 1166. A first PDCCH 1130 for CC 3600 c with the second transmission mode and/or carrier index may beassigned to the second transmission mode and/or carrier index searchspace beginning at the CCE location g. The first PDCCH for CC 3 canprovide the first PDSCH 1180 scheduling for CC 3. A second PDCCH 1132for CC 3 with the second different transmission mode and/or carrierindex may be assigned to the second different transmission mode and/orcarrier index search space at the CCE location after the first PDCCH forCC 3. The second PDCCH for CC 3 can provide the second PDSCH 1182scheduling for CC 3. In the illustration of FIG. 11, the PDCCHs for theCCs have an aggregation level of two.

The variable Y_(k) can be modified to utilize the transmission modes(T_(c,m)), the carrier index (CI), and the DCI size (S) input parametersfor the search space. Using an existing PDCCH assignment procedure, thetransmission modes (T_(c,m)), the carrier index (CI), and the DCI size(S), Y_(k) can be defined by Equation 5 to increase the number ofstarting addresses for a search spaces based on the transmission mode,CI, and S, where Y⁻¹=n_(RNTI)≠0, A=39827, D=65537, k=└n_(s)/2┘, andn_(s) is the slot number within the radio frame.Y _(k)=[A·(Y _(k−1)+ƒ(CI,T _(c,m) ,S))] mod D  [Equation 5]

The ƒ(CI,T_(c,m),S) can be a function of transmission modes T_(c,m) fora carrier (c), the carrier index (CI) in the DCI formats, and the DCIsize (S). The ƒ(CI,T_(c,m),S) can be an integer based on thetransmission modes (T_(c,m)), the carrier index (CI), and the DCI size(S). The DCI for a carrier may be allocated and mapped by an eNode B toCCEs in the PDCCH based on the transmission mode, the carrier index, andthe DCI size.

For example, the PDCCH for a subframe 610 on multiple CCs may betransmitted by CC 1 600 a, referred to as PDCCH1 1220, as illustrated inFIG. 12. A same transmission mode, carrier index, and DCI size searchspace 1250 starting location for a same transmission mode, carrierindex, and DCI size 1240 as CC 1 on an independent search space onPDCCH1 1218 may be calculated to be at a CCE location x 1262. Theindependent search space on PDCCH1 may have N CCEs (N_(CCE,k)) 1270 fora subframe (k). A first PDCCH 1222 for CC 1 with the same transmissionmode, carrier index, and DCI size as CC 1 may be assigned to the sametransmission mode, carrier index, and DCI size search space beginning atthe CCE location x. The first PDCCH for CC 1 can provide the first PDSCH1272 scheduling for CC 1. A second PDCCH 1224 for CC 1 with the sametransmission mode, carrier index, and DCI size as CC 1 may be assignedto the same transmission mode, carrier index, and DCI size search spaceat the CCE location after the first PDCCH for CC 1. The second PDCCH forCC 1 can provide the second PDSCH 1274 scheduling for CC 1.

A first different transmission mode, carrier index, and/or DCI sizesearch space 1252 starting location for a first different transmissionmode, carrier index, and/or DCI size 1242 different from thetransmission mode and/or carrier index of CC 1 on the independent searchspace on PDCCH1 may be calculated to be at a CCE location j 1264. Afirst PDCCH 1226 for CC 2 600 b with the different transmission mode,carrier index, and/or DCI size as CC 1 may be assigned to the firstdifferent transmission mode, carrier index, and/or DCI size search spacebeginning at the CCE location j. The first PDCCH for CC 2 can providethe first PDSCH 1276 scheduling for CC 2. A second PDCCH 1228 for CC 2with the first different transmission mode, carrier index, and/or DCIsize may be assigned to the first different transmission mode, carrierindex, and/or DCI size search space at the CCE location after the firstPDCCH for CC 2. The second PDCCH for CC 2 can provide the second PDSCH1278 scheduling for CC 2.

A second different transmission mode, carrier index, and/or DCI sizesearch space 1254 starting location for a second different transmissionmode, carrier index, and/or DCI size 1244 different from thetransmission mode and/or carrier index of CC 1 on the independent searchspace on PDCCH1 may be calculated to be at a CCE location g 1266. Afirst PDCCH 1230 for CC 3 600 c with the second transmission mode,carrier index, and/or DCI size may be assigned to the secondtransmission mode, carrier index, and/or DCI size search space beginningat the CCE location g. The first PDCCH for CC 3 can provide the firstPDSCH 1280 scheduling for CC 3. A second PDCCH 1232 for CC 3 with thesecond different transmission mode, carrier index, and/or DCI size maybe assigned to the second different transmission mode, carrier index,and/or DCI size search space at the CCE location after the first PDCCHfor CC 3. The second PDCCH for CC 3 can provide the second PDSCH 1282scheduling for CC 3. In the illustration of FIG. 12, the PDCCHs for theCCs have an aggregation level of two.

In another example illustrated by FIG. 13, an eNode B 1310 includes acoding unit 1334 and a scheduling unit 1332. The coding unit may map thePDCCH bits from a DCI message after performing CRC attachment (usingeach UE's RNTI 1336 a and 1136 b), channel coding, and rate matching.The scheduling unit may use the UE's RNTI, the UE's aggregation level,the transmission mode for each of the UE's CC, the carrier index foreach of the UE's CC, and/or the DCI size to schedule the CCEs of a PDCCHin a search space. The PDCCH can then be transmitted to the UEs. The UEs1320 a and 1320 b can have a searching unit 1342 a and 1342 b and adecoding unit 1342 a and 1342 b, respectively, for blind decoding aPDCCH search space. Each UE may use the UE's RNTI 1346 a and 1346 bassigned by the eNode B to de-mask or decode the PDCCH candidates in asearch space.

Another example provides a method 1400 for allocating a PDCCH to reducea number of PDCCH candidates in a search space for carrier aggregationon a UE, as shown in the flow chart in FIG. 14. The method includes theoperation of selecting 1410 a control channel element (CCE) aggregationlevel for a PDCCH allocation for each of a plurality of UEs at an eNodeB. The operation of identifying 1420 a transmission mode for each of aplurality of CCs associated with the PDCCH at the eNode B follows. Thenext operation of the method may be assigning 1430 each CC's DCI intoCCEs in a PDCCH search space in the PDCCH starting at a CCE locationbased on the CC's transmission mode and the CCE aggregation level forthe UE receiving the CC.

The method and system for allocating a PDCCH to reduce a number of PDCCHcandidates in a search space for carrier aggregation on a UE may beimplemented using a computer readable medium having executable codeembodied on the medium. The computer readable program code may beconfigured to provide the functions described in the method. Thecomputer readable medium may be a RAM, EPROM, flash drive, opticaldrive, magnetic hard drive, or other medium for storing electronic data.Additionally, the method and system for allocating a PDCCH to reduce anumber of PDCCH candidates in a search space for carrier aggregation ona UE may be downloaded as a computer program product transferred from aserver or eNode B to a requesting or wireless device by way of machinereadable data signals embodied in a carrier wave or other propagationmedium.

Various techniques, or certain aspects or portions thereof, may take theform of program code (i.e., instructions) embodied in tangible media,such as floppy diskettes, CD-ROMs, hard drives, or any othermachine-readable storage medium wherein, when the program code is loadedinto and executed by a machine, such as a computer, the machine becomesan apparatus for practicing the various techniques. In the case ofprogram code execution on programmable computers, the computing devicemay include a processor, a storage medium readable by the processor(including volatile and non-volatile memory and/or storage elements), atleast one input device, and at least one output device. One or moreprograms that may implement or utilize the various techniques describedherein may use an application programming interface (API), reusablecontrols, and the like. Such programs may be implemented in a high levelprocedural or object oriented programming language to communicate with acomputer system. However, the program(s) may be implemented in assemblyor machine language, if desired. In any case, the language may be acompiled or interpreted language, and combined with hardwareimplementations.

It should be understood that many of the functional units described inthis specification have been labeled as modules, in order to moreparticularly emphasize their implementation independence. For example, amodule may be implemented as a hardware circuit comprising custom VLSIcircuits or gate arrays, off-the-shelf semiconductors such as logicchips, transistors, or other discrete components. A module may also beimplemented in programmable hardware devices such as field programmablegate arrays, programmable array logic, programmable logic devices or thelike.

Modules may also be implemented in software for execution by varioustypes of processors. An identified module of executable code may, forinstance, comprise one or more physical or logical blocks of computerinstructions, which may, for instance, be organized as an object,procedure, or function. Nevertheless, the executables of an identifiedmodule need not be physically located together, but may comprisedisparate instructions stored in different locations which, when joinedlogically together, comprise the module and achieve the stated purposefor the module.

Indeed, a module of executable code may be a single instruction, or manyinstructions, and may even be distributed over several different codesegments, among different programs, and across several memory devices.Similarly, operational data may be identified and illustrated hereinwithin modules, and may be embodied in any suitable form and organizedwithin any suitable type of data structure. The operational data may becollected as a single data set, or may be distributed over differentlocations including over different storage devices, and may exist, atleast partially, merely as electronic signals on a system or network.The modules may be passive or active, including agents operable toperform desired functions.

Reference throughout this specification to “an example” means that aparticular feature, structure, or characteristic described in connectionwith the example is included in at least one embodiment of the presentinvention. Thus, appearances of the phrases “in an example” in variousplaces throughout this specification are not necessarily all referringto the same embodiment.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary. In addition, various embodiments and example of the presentinvention may be referred to herein along with alternatives for thevarious components thereof. It is understood that such embodiments,examples, and alternatives are not to be construed as defactoequivalents of one another, but are to be considered as separate andautonomous representations of the present invention.

Furthermore, the described features, structures, or characteristics maybe combined in any suitable manner in one or more embodiments. In thefollowing description, numerous specific details are provided, such asexamples of search spaces, to provide a thorough understanding ofembodiments of the invention. One skilled in the relevant art willrecognize, however, that the invention can be practiced without one ormore of the specific details, or with other methods, components,materials, etc. In other instances, well-known structures, materials, oroperations are not shown or described in detail to avoid obscuringaspects of the invention.

While the forgoing examples are illustrative of the principles of thepresent invention in one or more particular applications, it will beapparent to those of ordinary skill in the art that numerousmodifications in form, usage and details of implementation can be madewithout the exercise of inventive faculty, and without departing fromthe principles and concepts of the invention.

Accordingly, it is not intended that the invention be limited, except asby the claims set forth below.

What is claimed is:
 1. An apparatus of a user equipment (UE), theapparatus comprising: memory; and one or more processors configured to:monitor a set of physical downlink control channel (PDCCH) candidatesdefined in a search space S_(k) ^((L)) at an aggregation levelL∈{1,2,4,8} for a subframe (k), wherein the search space S_(k) ^((L)) isdefined by S_(k) ^((L))=L·{(Y_(k)+m)mod └N_(CCE,k)/L┘}+i whereinN_(CCE,k) is a total number of control channel elements (CCEs) in ak^(th) subframe (k∈{0,1,2,3,4,5,6,7,8,9}), i=0, . . . , L−1 is aconstant, m=0, . . . , M^((L))−1, and M^((L)) is a number of PDCCHcandidates to monitor in a given search space; and decode a PDCCH of theset of PDCCH candidates according to a downlink control information(DCI) format.
 2. The apparatus of claim 1, wherein the one or moreprocessors are further configured to determine PDCCH assignments of acellular communication system.
 3. The apparatus of claim 1, wherein theDCI format includes a carrier indicator field (CIF) value.
 4. Theapparatus of claim 1, wherein Y_(k) is defined by Y_(k)=(A·Y_(k−1))mod Dwherein, Y_(k−1)=n_(RNTI)≠0, n_(RNTI) is a Radio Network TemporaryIdentifier (RNTI) number assigned to the UE, A=39827, D=65537,k=└n_(s)/2┘, and n_(s)(n∈{0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19}) is a slot numberwithin a radio frame.
 5. The apparatus of claim 1, wherein the one ormore processors are further configured to: search for DCI associatedwith a selected component carrier (CC) in the search space S_(k) ^((L))by identifying a starting control channel elements (CCE) location basedon a selected CC's carrier index and the aggregation level L until avalidly decoded PDCCH candidate is decoded; and obtain the DCIassociated with the selected CC from the validly decoded PDCCHcandidate.
 6. The apparatus of claim 1, wherein a PDCCH candidateincludes a cyclic redundancy check (CRC) which is masked by a Cell-RadioNetwork Temporary Identifier (C-RNTI).
 7. A user equipment (UE)comprising: memory; and one or more processors configured to: monitor aset of physical downlink control channel (PDCCH) candidates defined in asearch space S_(k) ^((L)) at an aggregation level L∈{1,2,4,8} for asubframe (k), wherein the search space S_(k) ^((L)) is defined by S_(k)^((L))=L·{(Y_(k)+m)mod └N_(CCE,k)/L┘}+i wherein N_(CCE,k) is a totalnumber of control channel elements (CCEs) in a k^(th) subframe(k∈{0,1,2,3,4,5,6,7,8,9}), i=0, . . . , L−1 is a constant, m=0, . . . ,M^((L))−1, and M^((L)) is a number of PDCCH candidates to monitor in agiven search space; and decode a PDCCH of the set of PDCCH candidatesaccording to a downlink control information (DCI) format.
 8. The UE ofclaim 7, wherein the one or more processors are further configured todetermine PDCCH assignments of a cellular communication system.
 9. TheUE of claim 7, wherein the DCI format includes a carrier indicator field(CIF) value.
 10. The UE of claim 7, wherein Y_(k) is defined byY_(k)=(A·Y_(k−1))mod D wherein, Y_(k−1)=n_(RNTI)≠0, n_(RNTI) is a RadioNetwork Temporary Identifier (RNTI) number assigned to the UE, A=39827,D=65537, k=└n_(s)/2┘, and n_(s)(n∈{0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19}) is a slot numberwithin a radio frame.
 11. The UE of claim 7, wherein the one or moreprocessors are further configured to: search for DCI associated with aselected component carrier (CC) in the search space S_(k) ^((L)) byidentifying a starting control channel elements (CCE) location based ona selected CC's carrier index and the aggregation level L until avalidly decoded PDCCH candidate is decoded; and obtain the DCIassociated with the selected CC from the validly decoded PDCCHcandidate.
 12. The UE of claim 7, wherein a PDCCH candidate includes acyclic redundancy check (CRC) which is masked by a Cell-Radio NetworkTemporary Identifier (C-RNTI).
 13. At least one non-transitory machinereadable storage medium having instructions embodied thereon, theinstructions when executed by one or more processors of a user equipment(UE) perform the following: monitoring, at the UE, a set of physicaldownlink control channel (PDCCH) candidates defined in a search spaceS_(k) ^((L)) at an aggregation level L∈{1,2,4,8} for a subframe (k),wherein the search space S_(k) ^((L)) is defined by S_(k)^((L))=L·{(Y_(k)+m)mod └N_(CCE,k)/L┘}+i wherein N_(CCE,k) is a totalnumber of control channel elements (CCEs) in a k^(th) subframe(k∈{0,1,2,3,4,5,6,7,8,9}), i=0, . . . , L−1 is a constant, m=0, . . . ,M^((L))−1, and M^((L)) is a number of PDCCH candidates to monitor in agiven search space; and decoding, at the UE, a PDCCH of the set of PDCCHcandidates according to a downlink control information (DCI) format. 14.The at least one non-transitory machine readable storage medium of claim13, further comprising instructions when executed perform the following:determining PDCCH assignments of a cellular communication system. 15.The at least one non-transitory machine readable storage medium of claim13, wherein the DCI format includes a carrier indicator field (CIF)value.
 16. The at least one non-transitory machine readable storagemedium of claim 13, wherein Y_(k) is defined by Y_(k)=(A·Y_(k−1))mod Dwherein, Y_(k−1)=n_(RNTI)≠0, n_(RNTI) is a Radio Network TemporaryIdentifier (RNTI) number assigned to the UE, A=39827, D=65537,k=└n_(s)/2┘, and n_(s)(n∈{0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19}) is a slot numberwithin a radio frame.
 17. The at least one non-transitory machinereadable storage medium of claim 13, further comprising instructionswhen executed perform the following: searching for DCI associated with aselected component carrier (CC) in the search space S_(k) ^((L)) byidentifying a starting control channel elements (CCE) location based ona selected CC's carrier index and the aggregation level L until avalidly decoded PDCCH candidate is decoded; and obtaining the DCIassociated with the selected CC from the validly decoded PDCCHcandidate.
 18. The at least one non-transitory machine readable storagemedium of claim 13, wherein a PDCCH candidate includes a cyclicredundancy check (CRC) which is masked by a Cell-Radio Network TemporaryIdentifier (C-RNTI).